Semiconductor device

ABSTRACT

Disclosed is a semiconductor device including a first active pattern that extends in a first direction on an active region of a substrate, a first source/drain pattern in a recess on an upper portion of the first active pattern, a gate electrode that runs across a first channel pattern on the upper portion of the first active pattern and extends in a second direction intersecting the first direction, and an active contact electrically connected to the first source/drain pattern.

CROSS-REFERENCE TO RELATED APPLICATION

This U.S. nonprovisional application claims priority under 35 U.S.C §119 to Korean Patent Application No. 10-2019-0095991 filed on Aug. 7,2019 in the Korean Intellectual Property Office, the disclosures ofwhich are hereby incorporated by reference in their entirety.

BACKGROUND

The present inventive concepts relate to a semiconductor device, andmore particularly, to a semiconductor device including a field effecttransistor and a method of fabricating the same.

Semiconductor devices are beneficial in the electronic industry becauseof their small size, multi-functionality, and/or low fabrication cost.Semiconductor devices may encompass semiconductor memory devices storinglogic data, semiconductor logic devices processing operations of logicdata, and hybrid semiconductor devices having both memory and logicelements. Semiconductor devices have been increasingly required for highintegration with the advanced development of the electronic industry.For example, semiconductor devices have been increasingly requested forhigh reliability, high speed, and/or multi-functionality. Semiconductordevices have been gradually complicated and integrated to meet theserequested characteristics.

SUMMARY

Some example embodiments of the present inventive concepts provide asemiconductor device with improved electrical characteristics.

According to some example embodiments of the present inventive concepts,a semiconductor device includes a first active pattern that extends in afirst direction on a first active region of a substrate, a firstsource/drain pattern in a recess on an upper portion of the first activepattern, a gate electrode that runs across a first channel pattern onthe upper portion of the first active pattern, wherein the gateelectrode extends in a second direction different from the firstdirection and is provided on a top surface and at least one sidewall ofthe first channel pattern, and an active contact electrically connectedto the first source/drain pattern. The recess, when viewed in across-section of the first active pattern taken along the firstdirection, includes a first inner sidewall that extends, at a firstangle with respect to a bottom surface of the substrate, from a topsurface of the first active pattern toward the first channel pattern,and a second inner sidewall that extends, at a second angle with respectto the bottom surface of the substrate different from the first angle,from the first inner sidewall toward a bottom of the recess. The firstsource/drain pattern includes a first layer in a lower portion of therecess and a second layer on the first layer. The first layer covers thesecond inner sidewall. The second layer covers at least a portion of thefirst inner sidewall. The at least a portion of the first inner sidewallis exposed by the first layer. The first layer has a side part on thesecond inner sidewall and a central part on the bottom of the recess.The side part is at a height higher than a height at which the centralpart is. The first layer and the second layer include silicon-germanium(SiGe). A concentration of germanium (Ge) in the first layer is in arange from 10 at % to 45 at %. A concentration of germanium (Ge) in thesecond layer is in a range from 50 at % to 70 at %.

According to some example embodiments of the present inventive concepts,a semiconductor device includes a first active pattern, a second activepattern, and a third active pattern that are on an active region of asubstrate, wherein the first to third active patterns extend in parallelto each other in a first direction and are spaced apart from each otherin a second direction intersecting the first direction, a deviceisolation layer that is on the substrate and covers a lower sidewall ofeach of the first to third active patterns, wherein an upper portion ofeach of the first to third active patterns protrudes upwards from a topsurface of the device isolation layer, a source/drain patterncontinuously on the first to third active patterns, a gate electrodethat runs across the first to third active patterns, and an activecontact electrically connected to the source/drain pattern. Thesource/drain pattern includes first to third first layers on the firstto third active patterns respectively and spaced apart from each otherin the second direction, and a second layer continuously disposed on thefirst to third first layers. A height of the first first layer, whenviewed in a cross-section of the source/drain pattern taken along thesecond direction, is higher than a height of the second first layer. Aheight of the third first layer is higher than the height of the secondfirst layer. The first to third first layers and the second layerinclude silicon-germanium (SiGe). A concentration of germanium (Ge) ineach of the first to third first layers is in a range from 10 at % to 45at %. A concentration of germanium (Ge) in the second layer is in arange from 50 at % to 70 at %.

According to some example embodiments of the present inventive concepts,a semiconductor device includes an active pattern that extends in afirst direction on a PMOSFET region of a substrate, a device isolationlayer that is on the substrate and covers a lower sidewall of the activepattern, an upper portion of the active pattern protruding upwards froma top surface of the device isolation layer, a source/drain pattern in arecess between channels on the upper portion of the active pattern, agate electrode that runs across the upper portion of the active pattern,the gate electrode extending in a second direction different from thefirst direction, a first interlayer dielectric layer on the source/drainpattern and the gate electrode, a second interlayer dielectric layer onthe first interlayer dielectric layer, an active contact that penetratesthe first and second interlayer dielectric layers and has electricalconnection with the source/drain pattern, a gate contact that penetratesthe second interlayer dielectric layer and has electrical connectionwith the gate electrode, a silicide pattern between the source/drainpattern and the active contact, a third interlayer dielectric layer onthe second interlayer dielectric layer, a first connection line and asecond connection line in the third interlayer dielectric layer, a firstvia in the third interlayer dielectric layer that electrically connectsthe first connection line to the active contact, and a second via in thethird interlayer dielectric layer that electrically connects the secondconnection line to the gate contact. The recess, when viewed in across-section of the active pattern taken along the first direction,includes a first inner sidewall that extends, at a first angle withrespect to a bottom surface of the substrate, from a top surface of theactive pattern toward the channel, and a second inner sidewall thatextends, at a second angle with respect to the bottom surface of thesubstrate different from the first angle, from the first inner sidewalltoward a bottom of the recess. The source/drain pattern includes a firstlayer in a lower portion of the recess and a second layer on the firstlayer. The first layer covers the second inner sidewall. The secondlayer covers at least a portion of the first inner sidewall. The atleast a portion of the first inner sidewall is exposed by the firstlayer. The first layer includes a side part on the second inner sidewalland a central part on the bottom of the recess. The side part is at aheight higher than a height at which the central part is. The firstlayer and the second layer include silicon-germanium (SiGe). Aconcentration of germanium (Ge) in the first layer is in a range from 10at % to 45 at %. A concentration of germanium (Ge) in the second layeris in a range from 50 at % to 70 at %.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a plan view showing a semiconductor device accordingto some example embodiments of the present inventive concepts.

FIGS. 2A, 2B, 2C, and 2D illustrate cross-sectional views respectivelytaken along lines A-A′, B-B′, C-C′, and D-D′ of FIG. 1.

FIG. 3 illustrates an enlarged cross-sectional view showing section M ofFIG. 2A.

FIGS. 4, 6, 8, and 10 illustrate plan views showing a method offabricating a semiconductor device according to some example embodimentsof the present inventive concepts.

FIGS. 5, 7A, 9A, and 11A illustrate cross-sectional views taken alongline A-A′ of FIGS. 4, 6, 8, and 10, respectively.

FIGS. 7B, 9B, and 11B illustrate cross-sectional views taken along lineB-B′ of FIGS. 6, 8, and 10, respectively.

FIGS. 7C, 9C, and 11C illustrate cross-sectional views taken along lineC-C′ of FIGS. 6, 8, and 10, respectively.

FIG. 11D illustrates a cross-sectional view taken along line D-D′ ofFIG. 10.

FIG. 12 illustrates a cross-sectional view taken along line A-A′ of FIG.1, showing a semiconductor device according to some example embodimentsof the present inventive concepts.

FIG. 13 illustrates an enlarged cross-sectional view showing section Mof FIG. 12.

FIGS. 14A, 14B, 14C, and 14D illustrate cross-sectional viewsrespectively taken along lines A-A′, B-B′, C-C′, and D-D′ of FIG. 1,showing a semiconductor device according to some example embodiments ofthe present inventive concepts.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 illustrates a plan view showing a semiconductor device accordingto some example embodiments of the present inventive concepts. FIGS. 2A,2B, 2C, and 2D illustrate cross-sectional views respectively taken alonglines A-A′, B-B′, C-C′, and D-D′ of FIG. 1. FIG. 3 illustrates anenlarged cross-sectional view showing section M of FIG. 2A.

Referring to FIGS. 1, 2A to 2D, and 3, a substrate 100 may be providedwhich includes a first active region PR and a second active region NR.The substrate 100 may be a compound semiconductor substrate or asemiconductor substrate including silicon, germanium, silicon-germanium,or the like. For example, the substrate 100 may be a silicon substrate.

In an embodiment of the present inventive concepts, the first and secondactive regions PR and NR may each be a logic cell region that includeslogic transistors constituting a logic circuit of a semiconductordevice. For example, the logic cell region of the substrate 100 mayinclude logic transistors that constitute a logic circuit. The first andsecond active regions PR and NR may include at least one of the logictransistors. The first active region PR may be a positive (i.e.,p-channel) metal oxide semiconductor field effect transistor (PMOSFET)region, and the second active region NR may be a negative (i.e.,n-channel) metal oxide semiconductor field effect transistor (NMOSFET)region.

The first and second active regions PR and NR may be defined by a secondtrench TR2 formed on an upper portion of the substrate 100. The secondtrench TR2 may be positioned between the first and second active regionsPR and NR. The first and second active regions PR and NR may be spacedapart from each other in a first direction D1 across the second trenchTR2. Each of the first and second active regions PR and NR may extend ina second direction D2 intersecting the first direction D1.

First active patterns AP1 and second active patterns AP2 may berespectively provided on the first active region PR and the secondactive region NR. The first and second active patterns AP1 and AP2 mayextend in parallel to each other in the second direction D2. The firstand second active patterns AP1 and AP2 may be vertically protrudingportions of the substrate 100. A first trench TR1 may be defined betweenadjacent first active patterns AP1 and between adjacent second activepatterns AP2. The first trench TR1 may be shallower than the secondtrench TR2.

A device isolation layer ST may fill the first and second trenches TR1and TR2. The device isolation layer ST may include a silicon oxidelayer. The first and second active patterns AP1 and AP2 may have theirupper portions that protrude vertically upwards from the deviceisolation layer ST (see FIG. 2D). Each of the upper portions of thefirst and second active patterns AP1 and AP2 may have a fin shape. Forexample, the fin shape of each of the first and second active patternsAP1 and AP2 may protrude from a top surface of the substrate 100. Insome embodiments, the first and second active patterns AP1 and AP2 maybe part of the substrate 100, and in this manner, protruding from thesubstrate 100 refers to protruding past the top surface of the substrate100. The first and second active patterns AP1 and AP2 may be formedepitaxially from the top surface of the substrate or by patterning thesubstrate 100.

The device isolation layer ST may not cover the upper portions of thefirst active patterns AP1 or the upper portions of the second activepatterns AP2. The device isolation layer ST may cover lower sidewalls ofthe first and second active patterns AP1 and AP2.

First source/drain patterns SD1 may be provided on the upper portions ofthe first active patterns AP1. The first source/drain patterns SD1 maybe impurity regions having a first conductivity type (e.g., p-type). Afirst channel pattern CH1 may be interposed between a pair of firstsource/drain patterns SD1. Second source/drain patterns SD2 may beprovided on the upper portions of the second active patterns AP2. Thesecond source/drain patterns SD2 may be impurity regions having a secondconductivity type (e.g., n-type). A second channel pattern CH2 may beinterposed between a pair of second source/drain patterns SD2.

The first and second source/drain patterns SD1 and SD2 may be epitaxialpatterns formed by a selective epitaxial growth process. In an exampleembodiment, the first and second source/drain patterns SD1 and SD2 mayhave their top surfaces coplanar with those of the first and secondchannel patterns CH1 and CH2. In another example embodiment, the firstand second source/drain patterns SD1 and SD2 may have their top surfaceshigher than those of the first and second channel patterns CH1 and CH2.

The first source/drain patterns SD1 may include a semiconductor element(e.g., SiGe) whose lattice constant is greater than that of asemiconductor element (e.g., Si) of the substrate 100. In an exampleembodiment, SiGe may be an alloy with any molar ratio of silicon andgermanium, i.e., with a molecular formula of the form Si_((1-x))Ge_(x),where x is fractional number less than 1. The first source/drainpatterns SD1 may thus provide the first channel patterns CH1 withcompressive stress. For example, the second source/drain patterns SD2may include the same semiconductor element (e.g., Si) as that of thesubstrate 100.

Gate electrodes GE may be provided to extend in the first direction D1,while running across the first and second active patterns AP1 and AP2.The gate electrodes GE may be spaced apart from each other in the seconddirection D2. The gate electrodes GE may vertically overlap the firstand second channel patterns CH1 and CH2. Each of the gate electrodes GEmay surround the top surface and opposite sidewalls of each of the firstand second channel patterns CH1 and CH2.

Referring back to FIG. 2D, the gate electrode GE may be provided on afirst top surface TS1 of the first channel pattern CH1 and at least onefirst sidewall SW1 of the first channel pattern CH1. The gate electrodeGE may be provided on a second top surface TS2 of the second channelpattern CH2 and at least one second sidewall SW2 of the second channelpattern CH2. In this sense, a transistor according to the presentembodiment may be a three-dimensional field effect transistor such as afin field-effect transistor (FinFET) in which the first and secondchannel patterns CH1 and CH2 are three-dimensionally surrounded by thegate electrode GE.

Referring again to FIGS. 1, 2A to 2D, and 3, a pair of gate spacers GSmay be disposed on opposite sidewalls of each of the gate electrodes GE.The gate spacers GS may extend in the first direction D1 along the gateelectrodes GE. The gate spacers GS may have their top surfaces higherthan those of the gate electrodes GE. The top surfaces of the gatespacers GS may be coplanar with that of a first interlayer dielectriclayer 110 which will be discussed below. The gate spacers GS may includeone or more of SiCN, SiCON, and SiN. Alternatively, the gate spacers GSmay include a multiple layer including two or more of SiCN, SiCON, andSiN.

A gate capping pattern GP may be provided on each of the gate electrodesGE. The gate capping pattern GP may extend in the first direction D1along the gate electrode GE. The gate capping pattern GP may include amaterial having etch selectivity with respect to first and secondinterlayer dielectric layers 110 and 120 which will be discussed below.For example, the gate capping pattern GP may include one or more ofSiON, SiCN, SiCON, and SiN.

A gate dielectric pattern GI may be interposed between the gateelectrode GE and the first active pattern AP1 and between the gateelectrode GE and the second active pattern AP2. The gate dielectricpattern GI may extend along a bottom surface of the gate electrode GEthat overlies the gate dielectric pattern GI. For example, the gatedielectric pattern GI may cover the first top surface TS1 and the firstsidewall SW1 of the first channel pattern CH1. The gate dielectricpattern GI may cover the second top surface TS2 and the second sidewallSW2 of the second channel pattern CH2. The gate dielectric pattern GImay cover a top surface of the device isolation layer ST below the gateelectrode GE (see FIG. 2D).

In an embodiment of the present inventive concepts, the gate dielectricpattern GI may include a high-k dielectric material whose dielectricconstant is greater than that of a silicon oxide layer. For example, thehigh-k dielectric material may include one or more of hafnium oxide,hafnium silicon oxide, hafnium zirconium oxide, hafnium tantalum oxide,lanthanum oxide, zirconium oxide, zirconium silicon oxide, tantalumoxide, titanium oxide, barium strontium titanium oxide, barium titaniumoxide, strontium titanium oxide, lithium oxide, aluminum oxide, leadscandium tantalum oxide, and lead zinc niobate.

In another embodiment of the present inventive concepts, the gatedielectric pattern GI may include a ferroelectric. The gate dielectricpattern GI including the ferroelectric may serve as a negativecapacitor. For example, when the ferroelectric is supplied with anexternal voltage, there may be the occurrence of negative capacitanceeffect caused by phase change, from an initial polarization state to adifferent polarization state, resulting from migration of dipoles in theferroelectric. In this case, a transistor including the ferroelectricaccording to the present inventive concepts may have an increasedoverall capacitance, and accordingly may increase sub-threshold swingcharacteristics and may reduce operating voltage.

The ferroelectric of the gate dielectric pattern GI may include hafniumoxide doped with (or containing) one or more of zirconium (Zr), silicon(Si), aluminum (Al), and lanthanum (La). Because hafnium oxide is dopedwith one or more of zirconium (Zr), silicon (Si), aluminum (Al), andlanthanum (La) at a certain ratio, at least a portion of theferroelectric may have an orthorhombic crystal structure. When at leasta portion of the ferroelectric has the orthorhombic crystal structure,the negative capacitance effect may occur. The ferroelectric may have avolume ratio of 10% to 50% at its portion having the orthorhombiccrystal structure.

When the ferroelectric includes zirconium-doped hafnium oxide (ZrHfO), aratio of Zr atoms to Zr and Hf atoms, or a ratio of Zr/(Hf+Zr), may fallwithin a range from about 45 at % to about 55 at %. When theferroelectric includes silicon-doped hafnium oxide (SiHfO), a ratio ofsilicon (Si) atoms to silicon (Si) and hafnium (Hf) atoms, or a ratio ofSi/(Hf+Si), may fall within a range from about 4 at % to about 6 at %.When the ferroelectric includes aluminum-doped hafnium oxide (AlHfO), aratio of Al atoms to Al and Hf atoms, or a ratio of Al/(Hf+Al), may fallwithin a range from about 5 at % to about 10 at %. When theferroelectric includes lanthanum-doped hafnium oxide (LaHfO), a ratio ofLa atoms to La and Hf atoms, or a ratio of La/(Hf+La), may fall within arange from about 5 at % to about 10 at %.

The gate electrode GE may include a first metal pattern and a secondmetal pattern on the first metal pattern. The first metal pattern may beprovided on the gate dielectric pattern GI and adjacent to the first andsecond channel patterns CH1 and CH2. The first metal pattern may includea work function metal that controls a threshold voltage of a transistor.A thickness and composition of the first metal pattern may be adjustedto achieve a desired threshold voltage.

The first metal pattern may include a metal nitride layer. For example,the first metal pattern may include nitrogen (N) and at least one metalwhich is selected from titanium (Ti), tantalum (Ta), aluminum (Al),tungsten (W), and molybdenum (Mo). The first metal pattern may furtherinclude carbon (C). The first metal pattern may include a plurality ofwork function metal layers that are stacked.

The second metal pattern may include metal whose resistance is lowerthan that of the first metal pattern. For example, the second metalpattern may include one or more of tungsten (W), aluminum (Al), titanium(Ti), and tantalum (Ta).

A first interlayer dielectric layer 110 may be provided on the substrate100. The first interlayer dielectric layer 110 may cover the gatespacers GS and the first and second source/drain patterns SD1 and SD2.The first interlayer dielectric layer 110 may have a top surfacesubstantially coplanar with those of the gate capping patterns GP andthose of the gate spacers GS. The first interlayer dielectric layer 110may be provided thereon with a second interlayer dielectric layer 120covering the gate capping patterns GP. A third interlayer dielectriclayer 130 may be provided on the second interlayer dielectric layer 120.For example, the first, second, and third interlayer dielectric layers110, 120, and 130 may include a silicon oxide layer.

Active contacts AC may be provided to penetrate the first and secondinterlayer dielectric layers 110 and 120 and to correspondingly haveelectrical connection with the first and second source/drain patternsSD1 and SD2. Each of the active contacts AC may be provided between apair of gate electrodes GE.

The active contact AC may be a self-aligned contact. For example, thegate capping pattern GP and the gate spacer GS may be used to form theactive contact AC in a self-aligned manner. The active contact AC, forexample, may cover at least a portion of a sidewall of the gate spacerGS. Although not shown, the active contact AC may partially cover thetop surface of the gate capping pattern GP.

A silicide pattern SC may be interposed between the active contact ACand the first source/drain pattern SD1 and between the active contact ACand the second source/drain pattern SD2. The active contact AC may beelectrically connected through the silicide pattern SC to one of thefirst and second source/drain patterns SD1 and SD2. The silicide patternSC may include metal silicide, for example, one or more of titaniumsilicide, tantalum silicide, tungsten silicide, nickel silicide, andcobalt silicide.

The device isolation layer ST filling the second trench TR2 may beprovided thereon with at least one gate contact GC that penetrates thesecond interlayer dielectric layer 120 and the gate capping pattern GPand has electrical connection with the gate electrode GE.

Each of the active contact AC and the gate contact GC may include aconductive pattern FM and a barrier pattern BM that surrounds theconductive pattern FM. For example, the conductive pattern FM mayinclude one or more of aluminum, copper, tungsten, molybdenum, andcobalt. The barrier pattern BM may cover sidewalls and a bottom surfaceof the conductive pattern FM. The barrier pattern BM may include a metallayer and a metal nitride layer. The metal layer may include one or moreof titanium, tantalum, tungsten, nickel, cobalt, and platinum. The metalnitride layer may include one or more of a titanium nitride (TiN) layer,a tantalum nitride (TaN) layer, a tungsten nitride (WN) layer, a nickelnitride (NiN) layer, a cobalt nitride (CoN) layer, and a platinumnitride (PtN) layer.

A first wiring layer may be provided in the third interlayer dielectriclayer 130. The first wiring layer may include a plurality of connectionlines IL and a plurality of vias VI below the connection lines IL. Theconnection lines IL may extend in parallel to each other along thesecond direction D2. The connection lines IL may be arranged in thefirst direction D1.

The via VI may be provided between the active contact AC and a firstconnection line of the connection lines IL. The first connection linemay be electrically connected through the via VI to the active contactAC. The via VI may be provided between the gate contact GC and a secondconnection line of the connection lines IL. The second connection linemay be electrically connected through the via VI to the gate contact GC.

Although not shown, the first wiring layer may be provided with aplurality of stacked wiring layers. Logic cells may be connected to eachother through the connection lines IL and via VI, thereby constituting alogic circuit.

The first source/drain pattern SD1 will be further discussed in detailwith reference back to FIGS. 2A, 2C, and 3. A recess RS may be formed onthe upper portion of the first active pattern AP1. The recess RS may beformed between a pair of adjacent first channel patterns CH1. The firstsource/drain pattern SD1 may be provided in the recess RS.

The first source/drain pattern SD1 may include a buffer layer BL, a mainlayer ML on the buffer layer BL, and a capping layer CL on the mainlayer ML. In an embodiment of the present inventive concepts, the bufferlayer BL may include first and second semiconductor layers SL1 and SL2.The main layer ML may include third and fourth semiconductor layers SL3and SL4. The capping layer CL may include a fifth semiconductor layerSL5. In another embodiment of the present inventive concepts, the bufferlayer BL may be composed of one semiconductor layer. The main layer MLmay be composed of one semiconductor layer.

Referring back to FIG. 3, the first source/drain pattern SD1 will bedescribed based on its cross-section in the second direction D2. Therecess RS may include a pair of inner sidewalls RSw and a bottom RSbbetween the pair of inner sidewalls RSw. The inner sidewall RSw may havea first inner sidewall IS1 at an upper portion the recess RS and asecond inner sidewall IS2 that extends from the first inner sidewall IS1toward the bottom RSb.

The first inner sidewall IS1 may diagonally extend from a top surfaceAP1 t of the first active pattern AP1 toward the first channel patternCH1. The first inner sidewall IS1 may have a first angle θ1 relative toa bottom surface of the substrate 100. For example, the first angle θ1may range from about 30° to about 70°. A length of about 5 nm to about10 nm may be provided as a first depth TK1 from the top surface AP1 t(e.g., top surface of a fin) of the first active pattern AP1 to a firstlevel LV1 below the first inner sidewall IS1.

The second inner sidewall IS2 may extend downwards in a near-verticaldirection from the first inner sidewall IS1. The second inner sidewallIS2 may have a curved surface. An upper portion of the second innersidewall IS2 may have a second angle θ2 relative to the bottom surfaceof the substrate 100. The second angle θ2 may be measured at a secondlevel LV2 positioned at a second depth TK2 from the top surface AP1 t(or top surface of a fin) of the first active pattern AP1. The seconddept TK2 may be about 15 nm. The second angle θ2 may be greater thefirst angle θ1. The second angle θ2 may range from about 70° to about90°. In an example embodiment, at the first level LV1, the sidewall ofthe recess may be divided into the first inner sidewall IS1 and thesecond sidewall IS2. The first level LV1 may be defined as a boundary atwhich a sidewall slope angle of the recess may change from the firstangle θ1 to the second angle θ2.

The buffer layer BL may cover the inner sidewall RSw and the bottom RSbof the recess RS. The buffer layer BL may cover the second innersidewall IS2 of the recess RS, but may not cover the first innersidewall IS1 of the recess RS. The present invention is not limitedthereto. In an example embodiment, the buffer layer BL may not cover atleast a portion of the first inner sidewall IS1. The buffer layer BL mayexpose at least a portion of the first inner sidewall IS1.

The buffer layer BL may have a U shape when viewed in a cross-sectiontaken along the second direction D2. For example, the buffer layer BLmay include a side part SIP, extending upwardly along the second innersidewall IS1 in the recess, on the inner sidewall RSw of the recess RSand a central part CEP, covering the bottom RSb of the recess, on thebottom RSb of the recess RS. The central part CEP of the buffer layer BLmay have a top end at a first height H1, and the side part SIP of thebuffer layer BL may have a top end at a second height H2. The secondheight H2 may be higher than the first height H1. The first and secondheights H1 and H2 may be measured from a reference such as the lowestpart of the bottom RSb of the recess RS. A top end of the buffer layerBL may be at a lower level than that of the top surface AP1 t of thefirst active pattern AP1. For example, the top end of the buffer layerBL may be at the second level LV2.

The main layer ML may be provided on the buffer layer BL, therebycovering an inner sidewall of the main layer ML. The main layer ML mayfill the recess RS. The main layer ML may directly cover the first innersidewall IS1 of the recess RS, which first inner sidewall IS1 is notcovered with the buffer layer BL. The main layer ML may directly coverthe first inner sidewall IS1 of the recess RS, which first innersidewall IS1 is exposed by the buffer layer BL. The main layer ML mayhave a top surface that is substantially coplanar with or lower than thetop surface AP1 t of the first active pattern AP1.

The capping layer CL may be provided on the main layer ML. The cappinglayer CL may cover an exposed surface of the main layer ML. The cappinglayer CL may be conformally formed on the exposed surface of the mainlayer ML. The capping layer CL may protect the main layer ML.

Each of the buffer layer BL and the main layer ML may include asemiconductor element whose lattice constant is greater than that of asemiconductor element of the substrate 100. For example, when thesubstrate 100 includes silicon (Si), the buffer layer BL and the mainlayer ML may include silicon-germanium (SiGe). Germanium (Ge) may have alattice constant greater than that of silicon (Si).

The buffer layer BL may contain germanium (Ge) whose concentration isrelatively low. For example, the first semiconductor layer SL1 of thebuffer layer BL may contain germanium (Ge) whose concentration rangesabout 15 at % to about 25 at %. The second semiconductor layer SL2 ofthe buffer layer BL may contain germanium (Ge) whose concentration isgreater than that of germanium (Ge) contained in the first semiconductorlayer SL1. The second semiconductor layer SL2 may have a germaniumconcentration of about 25 at % to about 75 at %. In an exampleembodiment, the buffer layer BL may have a germanium concentration ofabout 10 at % to about 45 at %. The germanium concentration of thebuffer layer BL may increase along a third direction D3.

The main layer ML may contain germanium (Ge) whose concentration isrelatively high compared to the buffer layer BL. For example, the thirdsemiconductor layer SL3 of the main layer ML may have a germaniumconcentration of about 50 at % to about 60 at %. The fourthsemiconductor layer SL4 of the main layer ML may have a germaniumconcentration greater than that of the third semiconductor layer SL3.The germanium concentration of the fourth semiconductor layer SL4 mayrange from about 55 at % to about 70 at %. In conclusion, the main layerML may have a germanium concentration of about 50 at % to about 70 at %.The germanium concentration of the main layer ML may increase along thethird direction D3.

The buffer layer BL and the main layer ML may include impurities (e.g.,boron) that cause the first source/drain pattern SD1 to have a p-typeconductivity. The main layer ML may have an impurity concentration(e.g., atomic percent) greater than that of the buffer layer BL.

The buffer layer BL may prevent stacking faults between the main layerML and the substrate 100 (or the first active pattern AP1). Theoccurrence of stacking faults may increase channel resistance. Thestacking faults may most frequently occur on the bottom RSb of therecess RS. Therefore, to prevent the stacking faults, the central partCEP of the buffer layer BL may be formed to have a third thickness T3greater than a certain value. When a thickness of the buffer layer BLbecomes increased to prevent the stacking faults, the main layer ML mayhave a reduced volume in the recess RS. A reduction in volume of themain layer ML may reduce performance (e.g., resistance of source/drains)of PMOSFET.

According to some embodiments of the present inventive concepts, thebuffer layer BL may have the third thickness T3 greater than a certainvalue on the bottom RSb of the recess RS, and thus may prevent thestacking faults. Furthermore, the buffer layer BL may have a fourththickness T4, which is less than the third thickness T3, at its sidepart SIP on the inner sidewall RSw of the recess RS. For example, thebuffer layer BL is not formed on the first inner sidewall IS1 of therecess RS. The main layer ML may securely have a volume greater than acertain value in the recess RS.

Consequently, according to some embodiments of the present inventiveconcepts, the stacking faults may be prevented to reduce channelresistance of PMOSFET, and further a volume of the main layer ML may besufficiently obtained to increase performance of PMOSFET.

The fifth semiconductor layer SL5 of the capping layer CL may includethe same semiconductor element as that of the substrate 100. Forexample, the fifth semiconductor layer SL5 may includesingle-crystalline silicon (Si). The fifth semiconductor layer SL5 mayhave a silicon concentration of about 95 at % to about 100 at %. Thefifth semiconductor layer SL5 may have a germanium concentration ofabout 0 at % to about 5 at %. Germanium (Ge) contained in the fourthsemiconductor layer SL4 may diffuse into the fifth semiconductor layerSL5, and as a result, the fifth semiconductor layer SL5 may containgermanium (Ge) whose amount is extremely small (e.g., equal to or lessthan about 5 at %).

The first semiconductor layer SL1 on the bottom RSb of the recess RS mayhave a first thickness T1 less than a second thickness T2 of the secondsemiconductor layer SL2 on the bottom RSb of the recess RS. As discussedabove, the central part CEP of the buffer layer BL may have the thirdthickness T3. The third thickness T3 may be a sum of the first thicknessT1 and the second thickness T2.

As previously mentioned, the side part SIP of the buffer layer BL mayhave the fourth thickness T4 in the second direction D2. The fourththickness T4 may be measured at a third level LV3 positioned at a thirddepth TK3 from the top surface AP1 t (or top surface of a fin) of thefirst active pattern AP1. The third dept TK3 may be about 20 nm. At thethird level LV3, the first source/drain pattern SD1 may have a maximumwidth in the second direction D2. The fourth thickness T4 may be lessthan the third thickness T3. A ratio of the fourth thickness T4 to thethird thickness T3, or a ratio of T4/T3, may range from about 0.3 toabout 0.7.

Referring back to FIG. 2C, the first source/drain pattern SD1 will bedescribed based on its cross-section in the first direction D1. Thebuffer layer BL may be provided on each of the first active patternsAP1. The buffer layer BL on a first one of the first active patterns AP1may have a top surface at a fourth level LV4. The buffer layer BL on asecond one of the first active patterns AP1 may have a top surface at afifth level LV5. The buffer layer BL on a third one of the first activepatterns AP1 may have a top surface at the fourth level LV4. The fifthlevel LV5 may be lower than the fourth level LV4. In such cases, thebuffer layer BL on the second one of the first active patterns AP1 mayhave a height (or vertical length) less than that of the buffer layer BLon the first one of the first active patterns AP1. The height (orvertical length) of the buffer layer BL on the second one of the firstactive patterns AP1 may be less than that of the buffer layer BL on thethird one of the first active patterns AP1.

The main layer ML may be provided on the first active patterns AP1. Forexample, the main layers ML provided on corresponding first activepatterns AP1 may be integrally merged to form a single main layer ML onthe first active patterns AP1.

The main layer ML may include a first facet FA1, a second facet FA2, athird facet FA3, and a fourth facet FA4. The first to fourth facets FA1to FA4 may be surfaces of the third semiconductor layer SL3. The firstto fourth facets FA1 to FA4 may have crystal planes in the samecrystallographic space group such as {111} planes.

A sharp edge SE of the main layer ML may be defined by the first andsecond facets FA1 and FA2 or by the third and fourth facets FA3 and FA4.For example, the sharp edge SE may be a line formed where the first andsecond facets FA1 and FA2 meet each other or the third and fourth facetsFA3 and FA4. The sharp edge SE may horizontally extend in a directioncrossing a longitudinal direction (i.e., the second direction D2) of thefirst active pattern AP1. For example, the sharp edge SE may extendparallel to the second direction D2.

The capping layer CL may be provided on the main layer ML. The cappinglayer CL may cover the first to fourth facets FA1 to FA4 of the mainlayer ML. The capping layer CL may cover the sharp edge SE of the mainlayer ML. The first source/drain pattern SD1 may have a maximum width inthe first direction D1 at a level at which is located the sharp edge SEof the main layer ML.

The active contact AC and the silicide pattern SC may be provided on thefirst source/drain pattern SD1. In this case, the silicide pattern SCmay be in contact not only with the top surface of the main layer ML butwith a top surface of the capping layer CL. For example, the cappinglayer CL may increase a contact area between the first source/drainpattern SD1 and the silicide pattern SC. The increase in contact areamay be caused by a contact area between the silicide pattern SC and themain and capping layers ML and CL that is greater than that between thesilicide pattern SC and the main layer ML.

FIGS. 4, 6, 8, and 10 illustrate plan views showing a method offabricating a semiconductor device according to some example embodimentsof the present inventive concepts. FIGS. 5, 7A, 9A, and 11A illustratecross-sectional views taken along line A-A′ of FIGS. 4, 6, 8, and 10,respectively. FIGS. 7B, 9B, and 11B illustrate cross-sectional viewstaken along line B-B′ of FIGS. 6, 8, and 10, respectively. FIGS. 7C, 9C,and 11C illustrate cross-sectional views taken along line C-C′ of FIGS.6, 8, and 10, respectively. FIG. 11D illustrates a cross-sectional viewtaken along line D-D′ of FIG. 10.

Referring to FIGS. 4 and 5, a substrate 100 may be provided whichincludes a first active region PR and a second active region NR. Thesubstrate 100 may be patterned to form first and second active patternsAP1 and AP2. The present invention is not limited thereto. In an exampleembodiment, the first and second active patterns AP1 and AP2 may beepitaxially formed on the substrate 100. The first active patterns AP1may be formed on the first active region PR, and the second activepatterns AP2 may be formed on the second active region NR. A firsttrench TR1 may be formed between the first active patterns AP1 andbetween the second active patterns AP2.

The substrate 100 may be patterned to form a second trench TR2 betweenthe first active region PR and the second active region NR. The secondtrench TR2 may be formed deeper than the first trench TR1.

A device isolation layer ST may be formed on the substrate 100, fillingthe first and second trenches TR1 and TR2. The device isolation layer STmay include a dielectric material, such as a silicon oxide layer. Thedevice isolation layer ST may be recessed until upper portions of thefirst and second active patterns AP1 and AP2 are exposed. Thus, theupper portions of the first and second active patterns AP1 and AP2 mayprotrude vertically upwards from the device isolation layer ST.

Referring to FIGS. 6 and 7A to 7C, sacrificial patterns PP may be formedto run across the first and second active patterns AP1 and AP2. Each ofthe sacrificial patterns PP may be formed to have a linear or bar shapethat extends in a first direction D1. For example, the formation of thesacrificial patterns PP may include forming a sacrificial layer on anentire surface of the substrate 100, forming hardmask patterns MA on thesacrificial layer, and using the hardmask patterns MA as an etching maskto pattern the sacrificial layer. The sacrificial layer may include apolysilicon layer.

A pair of gate spacers GS may be formed on opposite sidewalls of each ofthe sacrificial patterns PP. The gate spacers GS may also be formed onopposite sidewalls of each of the first and second active patterns AP1and AP2. The opposite sidewalls of each of the first and second activepatterns AP1 and AP2 may be exposed portions that are covered neitherwith the device isolation layer ST nor with the sacrificial patterns PP.

The formation of the gate spacers GS may include conformally forming agate spacer layer on the entire surface of the substrate 100 andanisotropically etching the gate spacer layer. The gate spacer layer mayinclude one or more of SiCN, SiCON, and SiN. Alternatively, the gatespacer layer may be a multiple layer including two or more of SiCN,SiCON, and SiN.

Referring to FIGS. 8 and 9A to 9C, recesses RS may be formed on theupper portions of the first and second active patterns AP1 and AP2. Apair of recesses RS may be formed on opposite sides of each of thesacrificial patterns PP. The formation of the recesses RS may includeperforming an etching process in which the hardmask patterns MA and thegate spacers GS are used as an etching mask to etch the upper portionsof the first and second active patterns AP1 and AP2. When the etchingprocess is performed, the gate spacers GS may be removed from theopposite sidewalls of each of the first and second active patterns AP1and AP2. An exposed device isolation layer ST may be recessed during theetching process.

A first mask layer MP may be formed to selectively cover the secondactive patterns AP2. The first mask layer MP may selectively cover thesecond active region NR, but may expose the first active region PR. Thefirst mask layer MP may expose the first active patterns AP1.

First source/drain patterns SD1 may be formed to fill the recesses RS onthe first active patterns AP1 exposed by the first mask layer MP. Forexample, the formation of the first source/drain patterns SD1 mayinclude performing a selective epitaxial growth process in which innersidewalls of the recesses RS are used as seed layers. When the firstsource/drain patterns SD1 are formed, a first channel pattern CH1 may bedefined between a pair of first source/drain patterns SD1. For example,the selective epitaxial growth process may include a chemical vapordeposition (CVD) process or a molecular beam epitaxy (MBE) process.

The first source/drain pattern SD1 may include a second semiconductorelement whose lattice constant is greater than that of a firstsemiconductor element included of substrate 100. For example, the firstsemiconductor element may be silicon (Si), and the second semiconductorelement may be germanium (Ge). The first source/drain pattern SD1 may beformed of a plurality of semiconductor layers. The formation of thefirst source/drain pattern SD1 may include forming first to fifthsemiconductor layers SL1 to SL5 that are sequentially stacked. The firstand second semiconductor layers SL1 and SL2 may constitute a bufferlayer BL, the third and fourth semiconductor layers SL3 and SL4 mayconstitute a main layer ML, and the fifth semiconductor layer SL5 mayconstitute a capping layer CL.

The buffer layer BL may be formed by a first selective epitaxial growthprocess in which the inner sidewall of the recess RS on the first activepattern AP1 is used as a seed layer. The buffer layer BL may contain thesecond semiconductor element whose concentration is low. The bufferlayer BL may be doped to include low-concentrated impurities. Forexample, the buffer layer BL may include silicon-germanium (SiGe) dopedwith boron (B). The buffer layer BL may have a germanium concentrationof about 10 at % to about 45 at %.

Referring back to FIG. 3, the buffer layer BL may be formed to cover theinner sidewall RSw and the bottom RSb of the recess RS. The buffer layerBL may not cover at least a portion of the first inner sidewall IS1, butmay expose at least the portion of the first inner sidewall IS1. Duringthe first selective epitaxial growth process, a source gas may beprovided to grow the buffer layer BL, and an etching gas may also beprovided to suppress the growth of the buffer layer BL. The etching gasmay include HCl, Cl₂, or a combination thereof. A process condition(e.g., temperature, pressure, and flow rate of the etching gas) of thefirst selective epitaxial growth process may be controlled to allow thebuffer layer BL to grow without covering the first inner sidewall IS1 ofthe recess RS.

The main layer ML may be formed by a second selective epitaxial growthprocess in which the buffer layer BL is used as a seed layer. The mainlayer ML may contain the second semiconductor element whoseconcentration is high. The second semiconductor element contained in themain layer ML may have a concentration greater than that of the secondsemiconductor element contained in the buffer layer BL. The main layerML may be doped to include impurities whose concentration is higher thanthat that of impurities included in the buffer layer BL. For example,the main layer ML may include silicon-germanium (SiGe) doped with boron(B). The main layer ML may have a germanium concentration of about 50 at% to about 70 at %. Referring again to FIG. 3, the main layer ML may beformed to directly cover the first inner sidewall IS1 of the recess RS.The first inner sidewall IS1 thereof is exposed by the buffer layer BL.

The capping layer CL may be formed by a third selective epitaxial growthprocess in which the main layer ML is used as a seed layer. The cappinglayer CL may be formed to conformally cover a surface of the main layerML. The capping layer CL may include the same first semiconductorelement as that of the substrate 100. For example, the capping layer CLmay include single-crystalline silicon (Si). The capping layer CL mayhave a silicon concentration of about 95 at % to about 100 at %. In anembodiment, the third selective epitaxial growth process may beperformed at a lower temperature than those of the first and secondselective epitaxial growth processes.

Referring to FIGS. 10 and 11A to 11D, the first mask layer MP may beremoved. A second mask layer may be formed to selectively cover thefirst active patterns AP1. The second mask layer may selectively coverthe first active region PR, but may expose the second active region NR.The second mask layer may expose the second active patterns AP2.

Second source/drain patterns SD2 may be formed to fill the recesses RSon the second active patterns AP2 exposed by the second mask layer. Forexample, the formation of the second source/drain patterns SD2 mayinclude performing a selective epitaxial growth process in which exposedinner sidewalls of the recesses RS are used as seed layers. The secondsource/drain patterns SD2 may contain the same first semiconductorelement, such as silicon (Si), as that of the substrate 100. Thereafter,the second mask layer may be removed.

A first interlayer dielectric layer 110 may be formed to cover the firstand second source/drain patterns SD1 and SD2, the gate spacers GS, andthe mask patterns MA. For example, the first interlayer dielectric layer110 may include a silicon oxide layer.

A planarization process may be performed on the first interlayerdielectric layer 110 until top surfaces of the sacrificial patterns PPare exposed. An etch-back or chemical mechanical polishing (CMP) processmay be employed to planarize the first interlayer dielectric layer 110.As a result, the first interlayer dielectric layer 110 may have a topsurface substantially coplanar with those of the sacrificial patterns PPand those of the gate spacers GS.

Each of the sacrificial patterns PP may be replaced with a gateelectrode GE and a gate dielectric pattern GI. For example, the exposedsacrificial patterns PP may be selectively removed. The gate dielectricpattern GI may be formed in an empty space where the sacrificial patternPP is removed. The gate electrode GE may be formed on the gatedielectric pattern GI, filling the empty space.

The gate dielectric pattern GI may be conformally formed by an atomiclayer deposition (ALD) process and/or a chemical oxidation process. Thegate dielectric pattern GI may include, for example, a high-k dielectricmaterial. Alternatively, the gate dielectric pattern GI may include aferroelectric.

The formation of the gate electrode GE may include forming a gateelectrode layer on the gate dielectric pattern GI and planarizing thegate electrode layer. For example, the gate electrode layer may includea first gate electrode layer including metal nitride and a second gateelectrode layer including low-resistance metal.

An upper portion of the gate electrode GE may be selectively etched torecess the gate electrode GE. The recessed gate electrode GE may have atop surface lower than that of the first interlayer dielectric layer 110and those of the gate spacers GS. A gate capping pattern GP may beformed on the recessed gate electrode GE. The formation of the gatecapping pattern GP may include forming a gate capping layer that coversthe recessed gate electrode GE and planarizing the gate capping layeruntil the top surface of the first interlayer dielectric layer 110 isexposed. The gate capping layer may include, for example, one or more ofSiON, SiCN, SiCON, and SiN.

Referring back to FIGS. 1 and 2A to 2D, the second interlayer dielectriclayer 120 may be formed on the first interlayer dielectric layer 110.The active contacts AC may be formed to penetrate the second and firstinterlayer dielectric layers 120 and 110 and to have electricalconnection with the first and second source/drain patterns SD1 and SD2.The gate contact GC may be formed to penetrate the second interlayerdielectric layer 120 and the gate capping pattern GP and to haveelectrical connection with the gate electrode GE. The formation of theactive contacts AC and the gate contact GC may include forming thebarrier pattern BM that fills the contact hole and forming theconductive pattern FM on the barrier pattern BM.

The silicide pattern SC may be formed between the active contact AC andthe first source/drain pattern SD1 and between the active contact AC andthe second source/drain pattern SD2. The formation of the silicidepattern SC may include performing a silicidation process on the firstand second source/drain patterns SD1 and SD2. For example, the silicidepattern SC may include one or more of titanium silicide, tantalumsilicide, tungsten silicide, nickel silicide, and cobalt silicide.

The third interlayer dielectric layer 130 may be formed on the secondinterlayer dielectric layer 120. The first wiring layer may be formed inthe third interlayer dielectric layer 130. The formation of the firstwiring layer may include forming the plurality of connection lines ILand forming the plurality of vias VI below the connection lines IL. Theconnection lines IL and the vias VI may be formed by employing adamascene process or a dual damascene process.

FIG. 12 illustrates a cross-sectional view taken along line A-A′ of FIG.1, showing a semiconductor device according to some example embodimentsof the present inventive concepts. FIG. 13 illustrates an enlargedcross-sectional view showing section M of FIG. 12. In the embodimentthat follows, a detailed description of technical features repetitive tothose discussed above with reference to FIGS. 1, 2A to 2D, and 3 will beomitted, and a difference thereof will be discussed in detail.

Referring to FIGS. 1, 2B to 2D, 12, and 13, the buffer layer BL of thefirst source/drain pattern SD1 may cover a portion of the second innersidewall IS2 of the recess RS. The buffer layer BL may not cover atleast a portion of the second inner sidewall IS2 of the recess RS, butmay expose the at least a portion of the second inner sidewall IS2. Thebuffer layer BL may not cover the first inner sidewall IS1 of the recessRS. The main layer ML may directly cover the first inner sidewall IS1 ofthe recess RS and also directly cover at least a portion of the secondinner sidewall IS2 of the recess RS. The main layer ML may cover thefirst inner sidewall IS1 and at least the portion of the second innersidewall IS2 which are not covered with the buffer layer BL.

The buffer layer BL may not exist at the third level LV3 at which thefirst source/drain pattern SD1 has a maximum width in the seconddirection D2. For example, a ratio of the fourth thickness T4 to thethird thickness T3 discussed above in FIG. 3 may be zero. The side partSIP of the buffer layer BL on the second inner sidewall IS2 may have atop end at a third height H3. The third height H3 may be lower than thethird level LV3.

According to some embodiments of the present inventive concepts, becausethe buffer layer BL is selectively formed in a lower portion of therecess RS, the main layer ML may have a relatively large volume. As aresult, PMOSFETs may increase in performance.

FIGS. 14A, 14B, 14C, and 14D illustrate cross-sectional viewsrespectively taken along lines A-A′, B-B′, C-C′, and D-D′ of FIG. 1,showing a semiconductor device according to some example embodiments ofthe present inventive concepts. In the embodiment that follows, adetailed description of technical features repetitive to those formerlydiscussed with reference to FIGS. 1, 2A to 2D, and 3 will be omitted,and a difference thereof will be discussed in detail.

Referring to FIGS. 1 and 14A to 14D, the substrate 100 may be providedwhich includes a first active region PR and a second active region NR. Adevice isolation layer ST may be provided on the substrate 100. Thedevice isolation layer ST may define the first active patterns AP1 andsecond active patterns AP2 on an upper portion of the substrate 100. Thefirst active patterns AP1 and the second active patterns AP2 may berespectively defined on the first active region PR and the second activeregion NR.

Each of the first active patterns AP1 may be provided thereon with firstchannel patterns CH1 that are vertically stacked. The first channelpatterns CH1 stacked on the first active pattern AP1 may be spaced apartfrom each other in a third direction D3. The first channel patterns CH1stacked on the first active pattern AP1 may vertically overlap eachother.

Each of the second active patterns AP2 may be provided thereon withsecond channel patterns CH2 that are vertically stacked. The secondchannel patterns CH2 stacked on the second active pattern AP2 may bespaced apart from each other in the third direction D3. The secondchannel patterns CH2 stacked on the second active pattern AP2 mayvertically overlap each other. The first and second channel patterns CH1and CH2 may include one or more of silicon (Si), germanium (Ge), andsilicon-germanium (SiGe).

The first source/drain patterns SD1 may be provided on each of the firstactive patterns AP1. Recesses RS may be formed on the first activepattern AP1, and the first source/drain patterns SD1 may fillcorresponding recesses RS on the first active pattern AP1. The stackedfirst channel patterns CH1 may be interposed between a pair of adjacentfirst source/drain patterns SD1. The stacked first channel patterns CH1may connect the pair of adjacent first source/drain patterns SD1. Adescription of the first source/drain patterns SD1 according to thepresent embodiment may be substantially the same as that discussed abovewith reference to FIGS. 1, 2A to 2D, and 3.

The second source/drain patterns SD2 may be provided on each of thesecond active patterns AP2. Recesses RS may be formed on the secondactive pattern AP2, and the second source/drain patterns SD2 may fillcorresponding recesses RS on the second active pattern AP2. The stackedsecond channel patterns CH2 may be interposed between a pair of adjacentsecond source/drain patterns SD2. The stacked second channel patternsCH2 may connect the pair of adjacent second source/drain patterns SD2.

The gate electrodes GE may be provided to extend in a first directionD1, while running across the first and second channel patterns CH1 andCH2. The gate electrode GE may vertically overlap the first and secondchannel patterns CH1 and CH2. A pair of gate spacers GS may be disposedon opposite sidewalls of each of the gate electrodes GE. A gate cappingpattern GP may be provided on the gate electrode GE.

The gate electrode GE may surround each of the first and second channelpatterns CH1 and CH2 (see FIG. 14D). The gate electrode GE may beprovided on a first top surface TS1, at least one first sidewall SW1,and a first bottom surface BS1 of the first channel pattern CH1. Thegate electrode GE may be provided on a second top surface TS2, at leastone second sidewall SW2, and a second bottom surface BS2 of the secondchannel pattern CH2. For example, the gate electrode GE may surround atop surface, a bottom surface and opposite sidewalls of each of thefirst and second channel patterns CH1 and CH2. In this sense, atransistor according to the present embodiment may be athree-dimensional field effect transistor such as a multi-bridge channelfield effect transistor (MBCFET) in which the first and second channelpatterns CH1 and CH2 are three-dimensionally surrounded by the gateelectrode GE.

A gate dielectric pattern GI may be provided between the gate electrodeGE and each of the first and second channel patterns CH1 and CH2. Thegate dielectric pattern GI may surround each of the first and secondchannel patterns CH1 and CH2.

On the second active region NR, a dielectric pattern IP may beinterposed between the gate dielectric pattern GI and the secondsource/drain pattern SD2. The gate electrode GE may be spaced apart fromthe second source/drain pattern SD2 across the gate dielectric patternGI and the dielectric pattern IP. In contrast, no dielectric pattern IPmay be provided on the first active region PR.

A first interlayer dielectric layer 110 and a second interlayerdielectric layer 120 may be provided on an entire surface of thesubstrate 100. The active contacts AC may be provided to penetrate thefirst and second interlayer dielectric layers 110 and 120 and tocorrespondingly have connection with the first and second source/drainpatterns SD1 and SD2. The gate contact GC may be provided to penetratethe second interlayer dielectric layer 120 and the gate capping patternGP and to have connection with the gate electrode GE.

A third interlayer dielectric layer 130 may be provided on the secondinterlayer dielectric layer 120. The third interlayer dielectric layer130 may be provided therein with a first wiring layer including aplurality of connection lines IL and a plurality of vias VI.

A semiconductor device according to the present inventive concepts maybe configured such that source/drain patterns of PMOSFET may have theirbuffer layers that prevent stacking faults between active patterns andmain layers of the source/drain patterns. As a result, the PMOSFET maydecrease in channel resistance. Moreover, the main layer of thesource/drain pattern may securely have a volume greater than a certainvalue, which may result in an increase in performance of PMOSFET.

Although some example embodiments of the present inventive concepts havebeen discussed with reference to accompanying figures, it will beunderstood that various changes in form and details may be made thereinwithout departing from the spirit and scope of the present inventiveconcepts. It therefore will be understood that the embodiments describedabove are just illustrative but not limitative in all aspects.

What is claimed is:
 1. A semiconductor device, comprising: a firstactive pattern that extends in a first direction on a first activeregion of a substrate; a first source/drain pattern in a recess of anupper portion of the first active pattern; a gate electrode that runsacross a first channel pattern of the upper portion of the first activepattern, wherein the gate electrode extends in a second directiondifferent from the first direction and is provided on a top surface andat least one sidewall of the first channel pattern; and an activecontact electrically connected to the first source/drain pattern,wherein, the recess, when viewed in a cross-section of the first activepattern taken along the first direction, includes: a first innersidewall that extends, at a first angle with respect to a bottom surfaceof the substrate, from a top surface of the first active pattern towardthe first channel pattern; and a second inner sidewall that extends, ata second angle with respect to the bottom surface of the substratedifferent from the first angle, from the first inner sidewall toward abottom of the recess, the first source/drain pattern includes a firstlayer in a lower portion of the recess and a second layer on the firstlayer, the first layer covers the second inner sidewall, the secondlayer covers at least a portion of the first inner sidewall, the atleast a portion of the first inner sidewall being exposed by the firstlayer, the first layer has a side part on the second inner sidewall anda central part on the bottom of the recess, a height of the side partbeing higher than a height of the central part, the first layer and thesecond layer include silicon-germanium (SiGe), a concentration ofgermanium (Ge) in the first layer is in a range from 10 at % to 45 at %,and a concentration of germanium (Ge) in the second layer is in a rangefrom 50 at % to 70 at %.
 2. The semiconductor device of claim 1, whereinthe central part of the first layer has a first thickness, the side partof the first layer has a second thickness, and the first thickness isgreater than the second thickness.
 3. The semiconductor device of claim2, wherein the first source/drain pattern has a maximum width in thefirst direction at a first level, the second thickness is measured atthe first level, and a ratio of the second thickness to the firstthickness is in a range from 0.3 to 0.7.
 4. The semiconductor device ofclaim 1, wherein the first layer and the second layer stacked on eachother fill a space of the recess.
 5. The semiconductor device of claim1, wherein the second angle is greater than the first angle.
 6. Thesemiconductor device of claim 1, wherein the first source/drain patternfurther includes a third layer on the second layer, wherein aconcentration of silicon (Si) in the third layer is in a range from 95at % to 100 at %.
 7. The semiconductor device of claim 1, wherein thesecond layer covers the first inner sidewall and at least a portion ofthe second inner sidewall that is exposed by the first layer.
 8. Thesemiconductor device of claim 7, wherein the first source/drain patternhas a maximum width in the first direction at a first level, and theheight of the side part of the first layer is lower than the firstlevel.
 9. The semiconductor device of claim 1, further comprising: asecond active pattern that extends in the first direction on a secondactive region of the substrate; and a second source/drain pattern in arecess of an upper portion of the second active pattern, wherein thegate electrode runs across a second channel pattern of the upper portionof the second active pattern, wherein the first active region is aPMOSFET region, and wherein the second active region is an NMOSFETregion.
 10. The semiconductor device of claim 1, wherein the firstchannel pattern includes a plurality of first channel patterns that arevertically stacked, and the gate electrode surrounds a top surface, abottom surface, and opposite sidewalls of each of the plurality of firstchannel patterns.
 11. A semiconductor device, comprising: a first activepattern, a second active pattern, and a third active pattern that are onan active region of a substrate, wherein the first to third activepatterns extend in parallel to each other in a first direction and arespaced apart from each other in a second direction intersecting thefirst direction; a device isolation layer that is on the substrate andcovers a lower sidewall of each of the first to third active patterns,wherein an upper portion of each of the first to third active patternsprotrudes upwards from a top surface of the device isolation layer; asource/drain pattern continuously on the first to third active patterns;a gate electrode that runs across the first to third active patterns;and an active contact electrically connected to the source/drainpattern, wherein the source/drain pattern includes: first to third firstlayers on the first to third active patterns, respectively, and spacedapart from each other in the second direction; and a second layercontinuously disposed on the first to third first layers, a height ofthe first first layer, when viewed in a cross-section of thesource/drain pattern taken along the second direction, is higher than aheight of the second first layer, and a height of the third first layeris higher than the height of the second first layer, the first to thirdfirst layers and the second layer include silicon-germanium (SiGe), aconcentration of germanium (Ge) in each of the first to third firstlayers is in a range from 10 at % to 45 at %, and a concentration ofgermanium (Ge) in the second layer is in a range from 50 at % to 70 at%.
 12. The semiconductor device of claim 11, wherein the second layer,when viewed in a cross-section of the source/drain pattern taken alongthe second direction, has a first facet, a second facet, a third facet,and a fourth facet, a first edge is defined where the first facet andthe second facet meet each other, and a second edge is defined where thethird facet and the fourth facet meet each other.
 13. The semiconductordevice of claim 12, wherein the source/drain pattern further includes athird layer that covers the first to fourth facets of the second layer,wherein a concentration of silicon (Si) in the third layer is in a rangefrom 95 at % to 100 at %.
 14. The semiconductor device of claim 13,further comprising a silicide pattern between the source/drain patternand the active contact, wherein, when viewed in a cross-section of thesource/drain pattern taken along the second direction, the silicidepattern is in contact with a top surface of the second layer and a topsurface of the third layer.
 15. The semiconductor device of claim 11,wherein the second layer include a first second layer with the firstfacet, the second facet, a fifth facet and a sixth facet on the firstactive pattern, a second second layer with seventh to tenth facets onthe second active pattern, and a third second layer with the thirdfacet, the fourth facet, an eleventh facet, and a twelfth facet on thethird active pattern, and wherein the first second layer and the secondsecond layer are merged to each other and the second second layer andthe third second layer are merged to each other.
 16. A semiconductordevice, comprising: an active pattern that extends in a first directionon a PMOSFET region of a substrate; a device isolation layer that is onthe substrate and covers a lower sidewall of the active pattern, anupper portion of the active pattern protruding upwards from a topsurface of the device isolation layer; a source/drain pattern in arecess between channels on the upper portion of the active pattern; agate electrode that runs across the upper portion of the active pattern,the gate electrode extending in a second direction different from thefirst direction; a first interlayer dielectric layer on the source/drainpattern and the gate electrode; an active contact that penetrates thefirst interlayer dielectric layer and is electrically connected to thesource/drain pattern; a gate contact that penetrates the firstinterlayer dielectric layer and is electrically connected to the gateelectrode; a silicide pattern between the source/drain pattern and theactive contact; a second interlayer dielectric layer on the firstinterlayer dielectric layer; a first connection line and a secondconnection line in the second interlayer dielectric layer; a first viathat electrically connects the first connection line to the activecontact; and a second via that electrically connects the secondconnection line to the gate contact, wherein the recess, when viewed ina cross-section of the active pattern taken along the first direction,includes: a first inner sidewall that extends, at a first angle withrespect to a bottom surface of the substrate, from a top surface of theactive pattern toward the channel; and a second inner sidewall thatextends, at a second angle with respect to the bottom surface of thesubstrate different from the first angle, from the first inner sidewalltoward a bottom of the recess, wherein the source/drain pattern includesa first layer in a lower portion of the recess and a second layer on thefirst layer, the first layer covers the second inner sidewall, thesecond layer covers at least a portion of the first inner sidewall thatis exposed by the first layer, the first layer includes a side part onthe second inner sidewall and a central part on the bottom of therecess, a height of the side part being higher than a height of thecentral part, the first layer and the second layer includesilicon-germanium (SiGe), a concentration of germanium (Ge) in the firstlayer is in a range from 10 at % to 45 at %, and a concentration ofgermanium (Ge) in the second layer is in a range from 50 at % to 70 at%.
 17. The semiconductor device of claim 16, wherein the central part ofthe first layer has a first thickness, the side part of the first layerhas a second thickness, the source/drain pattern has a maximum width inthe first direction at a first level, the second thickness is measuredat the first level, and a ratio of the second thickness to the firstthickness is in a range from 0.3 to 0.7.
 18. The semiconductor device ofclaim 16, wherein the first and second layers stacked on each other filla space of the recess.
 19. The semiconductor device of claim 16, whereinthe source/drain pattern further includes a third layer stacked onsecond main layer, wherein a concentration of silicon (Si) in the thirdlayer is in a range from 95 at % to 100 at %.
 20. The semiconductordevice of claim 16, wherein the first layer includes a firstsemiconductor layer and a second semiconductor layer on the firstsemiconductor layer, wherein a concentration of germanium (Ge) in thesecond semiconductor layer is greater than a concentration of germanium(Ge) in the first semiconductor layer, the first semiconductor layer hasa first thickness on the bottom of the recess, the second semiconductorlayer has a second thickness on the bottom of the recess, and the secondthickness is greater than the first thickness.